Batch fermentation of glucose to ethanol yields a productivity of 4.5 g<sup>-1</sup>L h<sup>-1</sup>. If the yeast cell concentration in the fermentation broth is 5% (v/v) and the intracellular NAD<sup>+</sup>/NADH concentration in the yeast cells is 10 μM, the cycling rate of NAD<sup>+</sup> ⇌ NADH will be

Correct Answer: 20,000 cycles h<sup>-1</sup>